While fabric expansion joints are widely used in various systems, the exhaust systems of gas turbines present problems not satisfactorily met by expansion joints prior to the present invention.
Such problems arise from the fact that temperatures rise so rapidly as a turbine is started as to cause thermal shock a consequence of which may be the cause of cracked frames. Unless a joint ensures proper distribution of the high temperatures between the liners and the frames, binding and warping as well as the cracking of frames and liners may result. In addition, temperature differentials between internally and externally insulated duct secions of the system must be accommodated.
The various temperatures of the metal components of the joints and the different anchoring and mounting requirements of such components typically result in the requirement that expansion joints must be capable of absorbing not only axial movements but also movements in any direction normal to the flow path through the joint.
While the insulation of fabric expansion joints for use in the exhaust systems of gas turbines present particular requirements, it is the metal components of the joints that present major problems to the provision of joints capable of providing suitably long periods of proper service.